Chapter 23: Instrumentation for Motion Analysis

1. Chapter 23:Instrumentation for Motion Analysis KINESIOLOGY Scientific Basis of Human Motion, 10th edition Luttgens & Hamilton Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University

2. Objectives 1. Identify and describe instrumentation for the collection and analysis of kinematic data in human movement 2. Identify and describe instrumentation for the collection and analysis of kinetic data in human movement 3. Describe the limitation of biomechanical instrumentation 4. Critically examine the research literature in the field of human movement with an understanding of the methodologies used

3. Instrumentation of Kinematic Analysis • Data the describe a motion are collected with a variety of instruments • Cameras through high-speed film and video • Sophisticated motion tracking systems • Primary purpose is to enable people to analyze motion beyond the capabilities of their own physical senses

4. Instrumentation of Kinematic Analysis • Still cameras: multiple images on a single picture • Tiny lights on joint and extremities • Taken in a dark room with an open shutter • Motion appears as light streaks Fig 18.7

5. Instrumentation of Kinematic Analysis • Auto-advance cameras: • allowing rapid advancement and exposure Fig 23.1

6. Instrumentation of Kinematic Analysis • High-speed motion cameras: • Speed of 500 to 20,000 frames per second • Provide ample number of clear data point for analyzing the fastest of human motions • A projector that permits single frame projection so that measurements may be made of the image

7. Instrumentation of Kinematic Analysis • Electronic Digitizer: • The term digitize simply means that specific data points form each frame are input into the computer as pairs of x and y coordinates Fig 23.2

8. Instrumentation of Kinematic Analysis • Video: • Lower in cost that movie film and instant playback • May also be digitized • Two-dimensional or Three-dimensional

9. Basic Photoinstrumentation Procedures • Basic measurements in kinematics are time and displacement (both angular and linear) • Maximum accuracy of these measurements are important

10. Time • Based on the frame rate, or the rate at which images are photographed • Home movie camera: 24 frame/sec • Home video: 30 frames/sec • High-speed cameras: up to 20,000 frames/sec • Frame rate should be determined according to the speed at which an activity is performed • faster performance, higher frame rate • offer more detailed analysis

11. Displacement • Camera placement: 2-D perpendicular to the plane of motion • Scale references in the picture Fig 23.4

12. Other Photoinstrumentation Procedures • Camera must be absolutely level and still • a tripod and level are used • More light is required with higher shutter speeds • Markers on joints and body parts Fig 18.6

13. Optoeletronic Systems • Subject marked with light emitting diodes (LEDs) • cameras are sensitive to light sources and transmit their location is space to a computer as a series of x,y coordinates • Kinematic calculations are done based on changes in these coordinated

14. Optoeletronic Systems • Pictorial output usually is a stick figure Fig 23.4

15. Three-Dimensional (3D) Systems • Cameras systems configured to collect data in three planes • Analysis method is to position two cameras with perpendicular axes • Cameras must be carefully synchronized • System must be calibrated in 3D using a cube or a multi-armed device • Direct linear transformation is used for conversion of 2D pictures to a 3D image

16. Real Time Systems • Motion tracking system that operates in real time • Similar to virtual reality simulations • Currently light based or electromagnetic in nature

17. Electrogoniometer (elgon) and accelerometer • A double-arm goniometer with a potentiometer for an axis • angular displacement is electrical current • Accelerometer, measures linear acceleration Fig 23.6

18. Instrumentation for Kinetic Analysis • Usually collected through the use of • Dynamometers: spring and cable tension instruments that measure static muscle strength • grip strength dynamometer • Force transducers: one type is a strain gauge - altered resistance due to strain produces a change in output voltage which can be recorded

19. Adaptable Pressure Sensing Materials • Piezo electric film and force sensing resistors (FSRs) • variety of size • Connected to a computer with a analog to digital converter Fig 23.7

20. Force Plate • Senses ground reaction forces • Walking, running, jumping, landing, etc. • Linear forces and torques acting at the point of impact are identified

21. Electromyography (EMG) • Electrical activity (action potentials) from the muscles are sensed by surface or indwelling electrodes • Signal is amplified and transmitted to a recording device • Quantitative analysis by “normalizing” the EMG output Fig 23.9

22. Computer Models and Simulation • Kinematic, kinetic, and EMG data are compiled and synthesized into mathematical computer models • Allow for exploration of movement without endangering humans Fig 23.10

23. Computer Simulations • Used to predict limits of human performance Fig 23.11

24. Skeletal Muscle Simulation PE = Parallel elastic component SE = Series elastic component CE = Contractile element Fig 23.12

25. Using Quantitative Analysis • There should be some clear purpose in mind when one sets out to collect movement date, and will determine • Type of data collected • Methodology of collection • Instrumentation to collect • The analysis should be aimed toward some end result

26. Optimization of Performance • All factors which make up the motion are combined in such a was as to produce the most effective result • The goal of much of the quantitative biomechanical analysis • Provide mathematical description of the relationship between various factors that comprise the performance

27. Injury Prevention • Injuries are often the result of force applied in excessive or inappropriate ways • Quantitative data collection can provide valuable information about the risk of injury in any movement

28. Rehabilitation • In most therapeutic and rehabilitation setting, quantitative date are collected on patients on a regular basis • These data are then compared with models of normal patterns, and form these comparisons, programs of rehabilitation and remediation are designed